How to extract Youtube direct links.
       
       It works today, but may be broken tomorrow, there is no official API,
       links are hidden inside JS structures. It should be the reason why it is
       difficult to find any details on how to do that.
       
       Few online resources exist for the same. All have there own specifics,
       that is why I have found reasonable to get it in one more way.
       
       Youtube video pages contain a few <script> blocks. In one of them a specially
       crafted structure can be found that has an entry «url_encoded_fmt_stream_map».
       
       Decoding the value of this entry gives a list of direct URLs associated with
       the video page.
       
       Here is a utility to extract the list of direct video links, that works like this:
       
       $ parse-youtube 'https://www.youtube.com/watch?v=YE7VzlLtp-4'
       
       type: video/mp4;+codecs="avc1.64001F,+mp4a.40.2"
       qlty: hd720
       url:  http://r1---sn-1uxaxjvh-axqe.googlevideo.com/videoplayback?itag=22&mm=31&mime=video%2Fmp4&ip=5.19.241.250&expire=1420738590&key=yt5&signature=DB43337D5B7E07B87A078981A1BDDB0A8DD67315.CA1FC0C7C9026057BFB2D3EBA29612FAF7C6AE20&ms=au&ipbits=0&initcwndbps=3356250&mv=m&mt=1420716889&id=o-AGbOfROQYll24IOkksEs_RRk2pa7TsRnEWCnB74nstmd&upn=13Qhd3usVqw&sparams=dur%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Cmime%2Cmm%2Cms%2Cmv%2Cratebypass%2Csource%2Cupn%2Cexpire&sver=3&dur=596.567&source=youtube&ratebypass=yes&fexp=900504%2C900718%2C927622%2C930821%2C931024%2C932404%2C936931%2C9405619%2C941004%2C943917%2C947209%2C947218%2C948124%2C952302%2C952605%2C952901%2C955301%2C957103%2C957105%2C957201%2C958614%2C959701
       
       type: video/webm;+codecs="vp8.0,+vorbis"
       qlty: medium
       url:  http://r1---sn-1uxaxjvh-axqe.googlevideo.com/videoplayback?itag=43&mm=31&mime=video%2Fwebm&ip=5.19.241.250&expire=1420738590&key=yt5&signature=8AF71D47C2B663A7293A72CC7F61CD44D3185492.6BA2132AC05CB01355F0A92DAD02DAE2D1FFE5E1&ms=au&ipbits=0&initcwndbps=3356250&mv=m&mt=1420716889&id=o-AGbOfROQYll24IOkksEs_RRk2pa7TsRnEWCnB74nstmd&upn=13Qhd3usVqw&sparams=dur%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Cmime%2Cmm%2Cms%2Cmv%2Cratebypass%2Csource%2Cupn%2Cexpire&sver=3&dur=0.000&source=youtube&ratebypass=yes&fexp=900504%2C900718%2C927622%2C930821%2C931024%2C932404%2C936931%2C9405619%2C941004%2C943917%2C947209%2C947218%2C948124%2C952302%2C952605%2C952901%2C955301%2C957103%2C957105%2C957201%2C958614%2C959701
       
       Note that the page given with HTTPS, but the output links are HTTP.
       Both HTTP and HTTPS work, «hd720» URL for example:
       
       $ curl -sLI 'https://r1---sn-1uxaxjvh-axqe.googlevideo.com/videoplayback?itag=22&mm=31&mime=video%2Fmp4&ip=5.19.241.250&expire=1420738590&key=yt5&signature=DB43337D5B7E07B87A078981A1BDDB0A8DD67315.CA1FC0C7C9026057BFB2D3EBA29612FAF7C6AE20&ms=au&ipbits=0&initcwndbps=3356250&mv=m&mt=1420716889&id=o-AGbOfROQYll24IOkksEs_RRk2pa7TsRnEWCnB74nstmd&upn=13Qhd3usVqw&sparams=dur%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Cmime%2Cmm%2Cms%2Cmv%2Cratebypass%2Csource%2Cupn%2Cexpire&sver=3&dur=596.567&source=youtube&ratebypass=yes&fexp=900504%2C900718%2C927622%2C930821%2C931024%2C932404%2C936931%2C9405619%2C941004%2C943917%2C947209%2C947218%2C948124%2C952302%2C952605%2C952901%2C955301%2C957103%2C957105%2C957201%2C958614%2C959701' | grep -w 200
       
       HTTP/1.1 200 OK
       
       Content streamed in RTMPE is not eligible for direct downloading.
       
       The utility:
 (HTM) HTML
 (TXT) Plain-text